This invention relates to swaging tools for use in swaging fittings, and more particularly to a swaging tool for swaging axially swaged fittings, to join tubes or pipes.
Swaged fittings have been used for many years to connect tubes and pipes in various types of fluid systems, including those used in the aircraft, marine, petroleum and chemical industries. A tube end is inserted into a fitting, usually in the form of a cylindrical sleeve, and then the fitting is swaged with a swaging tool to produce a fluid-tight connection around the tube. This swaging operation usually is carried out by applying a radial force that radially compresses the fitting and tubing inwardly. The radial force may be applied directly by the swaging tool or indirectly by a specially shaped ring that is moved axially by the swaging tool to apply a radial force to the fitting. The present invention is directed to the latter type of swaging tool designed for use with fittings having axially movable swaging rings.
Typical axially swaged fittings comprise a cylindrical sleeve having openings at opposite ends for receiving the ends of two tubes to be connected, with a swaging ring at each end of the sleeve. The outer surface of the sleeve and the inner surface of the swaging ring which contact each other are shaped such that axial movement of the swaging ring over the sleeve applies a radial force to the sleeve and, thus, to the tubes. Although not all fittings employ a sleeve with two swaging rings, the use of two swaging rings is necessary when it is desired, as is often the case, to join two tubes to each other.
One type of swaging tool for axially swaged fittings includes a generally cylindrical housing having an inner surface and an outer surface, and a piston that is movable in opposite axial directions within the housing. The piston has a cylindrical outer surface in axial sliding engagement with the inner surface of the housing. The housing has a closed axial end and an open axial end where the open end is threaded and connected to a threaded cap, thereby enclosing the piston within the housing. The cap is connected to a source of hydraulic pressure for selectively moving the piston axially within the housing. A first engaging member is formed on the outer surface of the housing adjacent to the closed end for engaging one of the ring or the sleeve of the fitting to restrain it from axial movement. A second engaging member is formed on the outer surface of the piston for engaging the other one of the ring or the sleeve to move it in an axial direction toward the first engaging member upon movement of the piston toward the closed end of the housing.
While the above-described swaging tool works quite well, it does have its disadvantages. In particular, the housing is slotted to accommodate axial movement of the piston and second engaging member, which are integrally formed together, thereby retaining the second engaging member in place. Therefore, additional parts and structural support, such as a support ring to support the threaded end of the housing during swaging and gussets or legs to support the engaging members, are often necessary to maintain the structural integrity of the swaging tool. Additionally, it is not possible to easily modify or interchange the engaging members to accommodate differently sized swaged fittings.
Attempts have been made to create swaging tools that include relatively easily interchangeable engaging members. One available type of tool includes an elongated housing having an outer surface and defining an inner cylinder that receives a piston. A screw threaded end closure having a pressure fluid inlet closes the end of the cylinder. A piston is axially movable along only a portion of the bore adjacent a first end thereof, and a bar or guide shaft axially extends from a first end of the piston concentrically through the remaining portion of the bore towards a second end of the housing. A movable jaw unit is removably and slidably received on the guide shaft extending axially from the piston through an elongated aperture formed in the housing, and a fixed jaw unit is mounted to the housing second end in confronting relationship to the movable jaw unit. The junction between the shaft and the piston forms a radially extending load-bearing shoulder to support a portion of the movable jaw. A slide arm mounted to the movable jaw unit extends parallel to the cylinder and engages a longitudinal bearing surface on the outside of the cylinder to counteract deflection of the movable jaw unit during a swaging operation. The location of the slide arm along the outside of the cylinder, however, actually aggravates the deflection problem because it significantly increases the distance between the force generating axis (i.e., the piston axis) and the force application axis (i.e., the fitting axis), which, in turn, increases the bending moment on the movable jaw. In addition, as with the swaging tool described above, the threaded end cap requires occasional tightening and therefore increased maintenance of the tool. Moreover, the slide arm is complex to machine and adds undesired stresses to the movable jaw. Additionally, because the movable jaw is not affixed directly to the piston, the increased axial length of the housing prevents use of the tool in confined spaces.
Other types of axial swaging tools include movable jaw units mounted to the piston by a threaded fastener, which itself requires tightening. In addition, the movable jaw unit may include a pad that extends parallel to the cylinder to engage a longitudinal bearing surface on the outside of the cylinder. This pad, like the slide arm described above, increases the bending moment on the movable jaw because it increases the distance between the piston axis and the fitting axis. Another type of removable tool provides a removable jaw unit having a base attached to an annular sleeve for mounting about the outer circumference of a piston. To change the jaw, the entire piston must be disassembled. Moreover, existing tools include large numbers of components, making them complex to assemble and disassemble. Existing tools also require a relatively large retention force in a direction perpendicular to the center axis of the tool to affix the movable jaw in place. However, it has been found that only a small amount of force in a direction perpendicular to the tool center axis is necessary to retain the movable jaw in place. As a result, existing tools having removable or readily replaceable movable jaws are overly complex.
Thus, a swaging tool that includes readily interchangeable engaging members is desired that has fewer maintenance requirements, is lighter in weight, is more reliable in service, and also fits within confined spaces. Moreover, a tool is desired that includes sufficient frictional force in a direction perpendicular to the tool axis to locate the interchangeable engaging member in place.
The present invention is directed to an axial swaging tool having a readily replaceable movable jaw unit that utilizes frictional force to structurally retain the movable jaw in place, thereby providing a swaging tool that is extremely compact, includes fewer components, is simple to operate, and is lightweight.
The swaging tool includes a generally tubular housing having a first end portion including a port for providing pressurized fluid, a second end portion defining a closed cylinder and an intermediate portion therebetween that includes an elongated aperture through an outer surface of the housing. A single-piece piston is movably located within the housing, and axially extends through the intermediate housing portion such that at least a portion of the piston is visible through the aperture. A compression spring is interposed between a first end of the piston and the housing second end portion to bias the piston toward the housing first end portion. To maintain the spring in place, the piston first end includes an axial bore sized to receive a portion of the spring. A fixed jaw unit is located on the second end portion of the housing and a movable jaw unit is removably engageable directly to the piston.
In one embodiment, the piston includes a reduced external diameter portion axially located between two full diameter portions on the portion of the piston visible through the aperture. The movable jaw includes a base having two radially inwardly extending legs separated by a slot sized to fit about the reduced diameter portion of the piston. The axial length of the reduced diameter portion is slightly larger than the axial thickness of the movable jaw base, such that a tight interference fit is obtained when the base is radially inserted through the aperture to engage the piston reduced diameter portion. The two shoulders formed at the interfaces between the axially separated full diameter portions and the reduced diameter portion provide the required load-bearing support while reducing the bending moment on the movable jaw.
In a second embodiment, the piston includes a single radial bore perpendicular to the piston axis on a portion of the piston visible through the aperture. The movable jaw is generally Y-shaped, having a radially extending base leg that is sized to achieve a tight interference fit when inserted within the radial bore. Additionally, the axial bore that receives the compression spring may extend axially through the piston from the piston first end to the radial bore, thereby allowing the compression spring to exert an axial force on the base leg to position and retain the movable jaw. A detent attached to the spring may further frictionally engage a recess formed in the base leg to position and retain the movable jaw in place.
The swaging tool of the present invention therefore provides a movable jaw that is readily replaceable upon overcoming a slight frictional interference fit between the piston and the movable jaw or between a detent and the jaw. During assembly of a swaged fitting, however, the movable jaw base is completely supported by the piston itself, such that movement of the piston causes corresponding movement of the movable jaw. Moreover, since the piston itself moves in response to introduction of pressurized fluid, thereby moving the movable jaw directly, and since the movable jaw is attached directly to the piston, frictional losses within the tool are minimized, especially over prior art designs. Assembly of the tool is also simplified by minimizing the number of moving parts. Further, since the number of moving parts is reduced, the potential for frictional losses is minimized, while the size of the tool is likewise minimized.